TS6 & TSDown

[Pearce-Ropion]

Various changes and fixes to the build system

• Update to TS6
• Change build system to tsdown
  • Expose both cjs and esm builds
  • Added publint unused and attw plugins to ensure published package is correct
    • Removed react-dom since it was unused
• Add yarn types because the build system no longer runs type check
• Add separate typecheck job to CI
• Fix jest version mismatches
• Add __VERSION__ injection instead of importing package.json in runtime

[ryan-sigma]

is this to avoid us having .mjs as an extension for some reason?

[Pearce-Ropion]

Might not be necessary. I was having trouble getting attw to pass. I'll give it another go

[Pearce-Ropion]

Claude said this...

outExtensions is necessary because of "type": "module" in [package.json:7](vscode-webview://0mk05v0rhfbp3n674ov47ss8o9rrtckoum75g9addagbqjl3f4o9/package.json#L7).

With that field set, Node treats every .js file as ESM. So the CJS build can't use .js — it has to be .cjs, otherwise Node would try to load it as ESM at runtime and crash on require/module.exports.

The matching .d.cts for the CJS types is required for TypeScript's node16/nodenext module resolution. When a consumer does require('@sigmacomputing/plugin'), TS only picks up the CJS declaration if its extension lines up with the JS file (.cjs → .d.cts). The exports map in [package.json:11-22](vscode-webview://0mk05v0rhfbp3n674ov47ss8o9rrtckoum75g9addagbqjl3f4o9/package.json#L11-L22) is wired up the same way:

import → dist/esm/index.js + dist/esm/index.d.ts
require → dist/cjs/index.cjs + dist/cjs/index.d.cts
Without the override, tsdown would emit .js/.d.ts for both formats and the CJS half of the dual package would be broken — attw and publint (both enabled at [tsdown.config.ts:36-37](vscode-webview://0mk05v0rhfbp3n674ov47ss8o9rrtckoum75g9addagbqjl3f4o9/tsdown.config.ts#L36-L37)) would also fail.

But I tried removing it and it had no effect... so removing